The present invention relates to chemical compounds that inhibit P2X3 receptor. P2X purinoceptor 3 is a protein that in humans is encoded by the P2RX3 gene (Garcia-Guzman M, Stuhmer W, Soto F (September 1997). “Molecular characterization and pharmacological properties of the human P2X3 purinoceptor”. Brain Res Mol Brain Res 47 (1-2): 59-66). The product of this gene belongs to the family of purinoceptors for ATP. This receptor functions as a ligand-gated ion channel and transduces ATP-evoked nociceptor activation.
P2X purinoreceptors are a family of ligand-gated ion channels that are activated by ATP. To date, seven members of this family have been cloned, comprising P2X1-7 [Burnstock 2013, front Cell Neurosci 7:227]. These channels can exist as homomers and heteromers [Saul 2013, front Cell Neurosci 7:250]. Purines, such as ATP, have been recognized as important neurotransmitters and by acting via their respective receptors they have been implicated in various physiological and pathophysiological roles [Burnstock 1993, Drug Dev Res 28:196-206; Burnstock 2011, Prog Neurobiol 95:229-274; Jiang 2012, Cell Health Cytoskeleton 4:83-101].
Among the P2X family members, in particular the P2X3 receptor has been recognized as an important mediator of nociception [Burnstock 2013, Eur J Pharmacol 716:24-40; North 2003, J Phyiol 554:301-308; Chizh 2000, Pharmacol Rev 53:553-568]. It is mainly expressed in dorsal root ganglia in a subset of nociceptive sensory neurons. During inflammation the expression of the P2X3 receptor is increased, and activation of P2X3 receptor has been described to sensitize peripheral nerves [Fabretti 2013, front Cell Neurosci 7:236].
The prominent role of the P2X3 receptor in nociception has been described in various animal models, including mouse and rat models for acute, chronic and inflammatory pain. P2X3 receptor knock-out mice show a reduced pain response [Cockayne 2000, Nature 407:1011-1015; Souslova 2000, Nature 407:1015-1017]. P2X3 receptor antagonists have been shown to act anti-nociceptive in different models of pain and inflammatory pain [Ford 2012, Purin Signal 8 (Suppl 1):S3-S26]. The P2X3 receptor has also been shown to integrate different nociceptive stimuli. Hyperalgesia induced by PGE2, ET-1 and dopamine have all been shown to be mediated via release of ATP and activation of the P2X3 receptor [Prado 2013, Neuropharm 67:252-258; Joseph 2013, Neurosci 232C: 83-89].
Besides its prominent role in nociception and in pain-related diseases involving both chronic and acute pain, the P2X3 receptor has been shown to be involved in genitourinary, gastrointestinal and respiratory conditions and disorders, including overactive bladder and chronic cough [Ford 2013, front Cell Neurosci 7:267; Burnstock 2014, Purin Signal 10(1):3-50]. ATP-release occurs in these 2 examples from epithelial cells, which in turn activates the P2X3 receptor and induces contraction of bladder and lung muscles respectively leading to premature voiding or cough.
P2X3 subunits do not only form homotrimers but also heterotrimers with P2X2 subunits. P2X3 subunits and P2X2 subunits are also expressed on nerve fibres innervating the tongue, therein taste buds [Kinnamon 2013, front Cell Neurosci 7:264].
In a phyiosological setting, receptors containing P2X3 and/or P2X2 subunits are involved in the transmission of taste from the tongue (bitter, sweet, salty, umami and sour). Recent data show that while blocking the P2X3 homomeric receptor alone is important to achieve anti-nociceptive efficacy, non-selective blockade of both the P2X3 homomeric receptor and the P2X2/3 heteromeric receptor leads to changes in taste perception which might limit the therapeutic use of non-selective P2X3 and P2X2/3 receptor antagonists [Ford 2014, purines 2014, abstract book p15]. Therefore, compounds that differentiate between P2X3 and P2X2/3 receptors are highly desirable.
Compounds blocking both the exclusively P2X3 subunit containing ion channel (P2X3 homomer) as well as the ion channel composed of P2X2 and P2X3 subunit (P2X2/3 heterotrimer) are called P2X3 and P2X2/3 nonselective receptor antagonists [Ford, Pain Manag 2012]. Clinical Phll trials demonstrated that AF-219, a P2X3 antagonist, leads to taste disturbances in treated subjects by affecting taste sensation via the tongue [e.g. Abdulqawi et al, Lancet 2015; Strand et al, 2015 ACR/ARMP Annual Meeting, Abstract 2240]. This side effect has been attributed to the blockade of P2X2/3 channels, i.e. the heterotrimer [A. Ford, London 2015 Pain Therapeutics Conference, congress report]. Both P2X2 and P2X3 subunits are expressed on sensory nerve fibers innervating the tongue. Knock-out animals deficient for P2X2 and P2X3 subunits show reduced taste sensation and even taste loss [Finger et al, Science 2005], whereas P2X3 subunit single knock-outs exhibit a mild or no change in phenotype with respect to taste. Moreover, 2 distinct populations of neurons have been described in the geniculate ganglion expressing either P2X2 and P2X3 subunits or P2X3 subunit alone. In an in vivo setting assessing taste preference towards an artificial sweetener via a lickometer, only at very high free plasma levels (>100 μM) effects on taste were observed, indicating that rather the P2X2 and P2X3 subunits expressing population plays a major role in taste sensation than the P2X3 subunit expressing population [Vandenbeuch et al, J Physiol. 2015]. Hence, as a modified taste perception has profound effects on the quality of life of patients, P2X3-homomeric receptor-selective antagonists are deemed to be superior towards non-selective receptor antagonists and are considered to represent a solution towards the problem of insufficient patient compliance during chronic treatment as indicated by increased drop-out rates during Phll trials [Strand et al, 2015 ACR/ARMP Annual Meeting, Abstract 2240 and A. Ford, London 2015 Pain Therapeutics Conference, congress report].
Benzamide derivative compounds have been disclosed in prior art for the treatment or prophylaxis of different diseases: WO2009/058298 and WO2009/058299 (Merck) disclose novel P2X3 type receptor antagonists which have a benzamide core structure substituted with a phenyl or pyridyl moiety, but not a thiazole, rendering said compounds different from the compounds of the present invention.
WO2008/000645 (Roche) addresses P2X3 and/or P2X2/3 receptor antagonist compounds useful for the treatment of diseases associated with P2X purinergic receptors. According to the general formula of claim 1, the benzamide compounds are substituted with tetrazole. Furthermore, they may be having substituents like phenyl, pyridinyl, pyrimidinyl, pyridazinyl or thiophenyl. However, there is no thiazolyl substituent disclosed.
WO2009/077365, WO2009/077366, WO2009/077367 and WO2009/077371 (Roche) disclose a series of benzamide derivatives either substituted with imidazole, triazole, pyrazole or tetrazole which are stated to be useful for treatment of diseases associated with P2X purinergic receptors, and more particularly to P2X3 receptor and/or P2X2/3 receptor antagonists. According to the general formula of claim 1, the benzamide compounds may have additional substituents R6, R7 and R8 being C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, halogen atoms or cyano. However, ethers substituted with the functional groups like —C2-C6-alkyl-OR4, —(CH2)q—(C3-C7-cycloalkyl), —(CH2)q-(6- to 12-membered heterobicycloalkyl), —(CH2)q-(4- to 7-membered heterocycloalkyl), —(CH2)q-(5- to 10-membered heteroaryl) or —C2-C6-alkynyl are not disclosed.
US20100152203 (Roche) discloses substituted benzamides with R1 being thiadiazolyl and R2 being phenyl, pyridinyl, pyrimidinyl, pyridazinyl, or thiophenyl as compounds useful for treatment of diseases associated with P2X purinergic receptors, and more particularly relates to P2X3 receptor and/or P2X2/3 receptor antagonists usable for treatment of genitourinary, pain, inflammatory, gastrointestinal and respiratory diseases, conditions and disorders. More specifically, the benzamide compounds may be additionally substituted with C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, halogen atoms or cyano. However, ethers substituted with the functional groups like —C2-C6-alkyl-OR4, —(CH2)q—(C3-C7-cycloalkyl), —(CH2)q-(6- to 12-membered heterobicycloalkyl), —(CH2)q-(4- to 7-membered heterocycloalkyl), —(CH2)q-(5- to 10-membered heteroaryl) or —C2-C6-alkynyl are not disclosed.
US20100324056 (Roche) discloses substituted benzamides with R1 being phenyl, thienyl, pyrimidinyl, pyridazinyl, or pyridinyl as compounds useful for treatment of diseases associated with P2X purinergic receptors, and more particularly relates to P2X3 receptor and/or P2X2/3 receptor antagonists usable for treatment of genitourinary, pain, inflammatory, gastrointestinal and respiratory diseases, conditions and disorders. Ethers substituted with the functional groups like —C2-C6-alkyl-OR4, —(CH2)q—(C3-C7-cycloalkyl), —(CH2)q-(6- to 12-membered heterobicycloalkyl), —(CH2)q-(4- to 7-membered heterocycloalkyl), —(CH2)q-(5- to 10-membered heteroaryl) or —C2-C6-alkynyl are not disclosed.
US20100324069 (Genentech) discloses oxazolone- and pyrrolidinone-substituted benzamides and their use for the prophylaxis and/or treatment of diseases which are associated with P2X3 receptor and/or P2X2/3 receptor antagonists. According to the general formula of claim 1 the benzamide compounds are additional substituted with a pyridine or phenyl. Ether-bearing groups at the benzamide core structure are not disclosed.
WO2006119504 (Renovis) relates to fused heterocyclic compounds of the class tetrahydronaphthyridines and tetrahydropyrido[4,3-d]pyrimidines and to pharmaceutical compositions containing such compounds.
WO2008123963 (Renovis) relates to fused heterocyclic compounds of the class tetrahydropyrido[4,3-d]pyrimidines and pharmaceutical compositions comprising such compounds. Also provided are methods for preventing and/or treating conditions in mammals, such as (but not limited to) arthritis, Parkinson's disease, Alzheimer's disease, asthma, myocardial infarction, pain syndromes (acute and chronic or neuropathic), neurodegenerative disorders, schizophrenia, cognitive disorders, anxiety, depression, inflammatory bowel disease and autoimmune disorders, and promoting neuroprotection, using the fused heterocyclic compounds and pharmaceutical compositions thereof.
WO2008130481 (Renovis) discloses 2-cyanophenyl fused heterocyclic compounds of the class tetrahydropyrido[4,3-d]pyrimidines and pharmaceutical compositions comprising such compounds.
WO2010033168 (Renovis) discloses a series of benzamides substituted with phenyl or pyridyl which are stated to be useful for treatment of diseases associated with P2X purinergic receptors, and more particularly to P2X3 receptor and/or P2X2/3 receptor antagonists. However, benzamides with additional ether groups are not disclosed.
WO2009110985 (Renovis) relates to phenyl- and pyridyl-substituted benzamide compounds and pharmaceutical compositions comprising such compounds, but not thiazole-substituted benzamides, rendering said compounds different from the compounds of the present invention.
WO2008/055840 (Roche) relates to thiazol- and oxazole-substituted benzamides substituted with R2 being phenyl, pyridinyl, pyrimidinyl, pyridazinyl or thiophenyl that can be used for treating diseases associated with P2X purinergic receptors, and more particularly as P2X3 and/or P2X2/3 receptor antagonists. However, the thiazole substituted benzamides have in fact C1-C6-alkyl, C1-C6-alkoxy, C1-C6-haloalkyl, halo-C1-C6-alkoxy groups, halogen atoms or cyano, but ethers substituted with the functional groups like —C2-C6-alkyl-OR4, —(CH2)q—(C3-C7-cycloalkyl), —(CH2)q-(6- to 12-membered heterobicycloalkyl), —(CH2)q-(4- to 7-membered heterocycloalkyl), —(CH2)q-(5- to 10-membered heteroaryl) or —C2-C6-alkynyl are not disclosed.
So, the state of the art described above does not describe the specific thiazole substituted benzamide compounds of general formula (I) of the present invention as defined herein or an isomer, enantiomer, diastereomer, racemate, hydrate, solvate, or a salt thereof, or a mixture of same, as described and defined herein, and as hereinafter referred to as “compounds of the present invention”, or their pharmacological activity.
It has now been found, and this constitutes the basis of the present invention, that said compounds of the present invention have surprising and advantageous properties.
In particular, said compounds of the present invention have surprisingly been found to effectively inhibit the P2X3 receptor and may therefore be used for the treatment or prophylaxis of following diseases:                genitourinary, gastrointestinal, respiratory and pain-related diseases, conditions and disorders;        gynecological diseases including dysmenorrhea (primary and secondary dysmenorrhea), dyspareunia, endometriosis, and adenomyosis; endometriosis-associated pain; endometriosis-associated symptoms, wherein said symptoms are in particular dysmenorrhea, dyspareunia, dysuria, or dyschezia; endometriosis-associated proliferation; pelvic hypersensitivity;        urinary tract disease states associated with the bladder outlet obstruction; urinary incontinence conditions such as reduced bladder capacity, increased frequency of micturition, urge incontinence, stress incontinence, or bladder hyperreactivity; benign prostatic hypertrophy; prostatic hyperplasia; prostatitis; detrusor hyperreflexia; overactive bladder and symptoms related to overactive bladder wherein said symptoms are in particular increased urinary frequency, nocturia, urinary urgency or urge incontinence; pelvic hypersensitivity; urethritis; prostatitis; prostatodynia; cystitis, in particular Interstitial cystitis; idiopathic bladder hypersensitivity [Ford 2014, purines 2014, abstract book p15];        pain syndromes (including acute, chronic, inflammatory and neuropathic pain), preferably inflammatory pain, low back pain surgical pain, visceral pain, dental pain, periodontitis, premenstrual pain, endometriosis-associated pain, pain associated with fibrotic diseases, central pain, pain due to burning mouth syndrome, pain due to burns, pain due to migraine, cluster headaches, pain due to nerve injury, pain due to neuritis, neuralgias, pain due to poisoning, pain due to ischemic injury, pain due to interstitial cystitis, cancer pain, pain due to viral, parasitic or bacterial infections, pain due to traumatic nerve-injury, pain due to post-traumatic injuries (including fractures and sport injuries), pain due to trigeminal neuralgia, pain associated with small fiber neuropathy, pain associated with diabetic neuropathy, postherpetic neuralgia, chronic lower back pain, neck pain phantom limb pain, pelvic pain syndrome, chronic pelvic pain, neuroma pain, complex regional pain syndrome, pain associated with gastrointestinal distension, chronic arthritic pain and related neuralgias, and pain associated with cancer, Morphine-resistant pain, pain associated with chemotherapy, HIV and HIV treatment-induced neuropathy; and pain associated with diseases or disorders selected from the group consisting of hyperalgesia, allodynia, functional bowel disorders (such as irritable bowel syndrome) and arthritis (such as osteoarthritis, rheumatoid arthritis and ankylosing spondylitis);        Epilepsy, partial and generalized seizures;        Respiratory disorders including chronic obstructive pulmonary disorder (COPD) [Ford 2013, European Respiratory Society Annual Congress 2013], asthma [Ford 2014, 8th Pain&Migraine Therapeutics Summit], bronchospasm, pulmonary fibrosis, acute cough, chronic cough including chronic idiopathic and chronic refractory cough;        Gastrointestinal disorders including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), biliary colic and other biliary disorders, renal colic, diarrhea-dominant IBS, gastroesophageal reflux, gastrointestinal distension, Crohn's disease and the like;        neurodegenerative disorders such as Alzheimer's disease, Multiple Sclerosis, Parkinson's disease, Brain ischemia and traumatic brain injury;        myocardial infarction, lipid disorders;        pain-associated diseases or disorders selected from the group consisting of hyperalgesia, allodynia, functional bowel disorders (such as irritable bowel syndrome), gout, arthritis (such as osteoarthritis [Ford 2014, 8th Pain&Migraine Therapeutics Summit], rheumatoid arthritis and ankylosing spondylitis), burning mouth syndrome, burns, migraine or cluster headaches, nerve injury, traumatic nerve injury, post-traumatic injuries (including fractures and sport injuries), neuritis, neuralgias, poisoning, ischemic injury, interstitial cystitis, cancer, trigeminal neuralgia, small fiber neuropathy, diabetic neuropathy, chronic arthritis and related neuralgias, HIV and HIV treatment-induced neuropathy, pruritus; impaired wound healing and disease of the skeleton like degeneration of the joints        pruritus.        
The compounds of the present invention show high P2X3 receptor inhibition and furthermore selectivity over the P2X2/3 receptor. Selective inhibition of the P2X3 receptor over the P2X2/3 receptor means at least 3-fold selectivity over the P2X2/3 receptor. Preferred compounds of the present invention show at least 10-fold selectivity over the P2X2/3 receptor. In addition to that, more preferred compounds of the present invention show further advantageous properties that are beneficial for their use as medicaments, such as desirable pharmacokinetic profiles that provide suitable metabolic stability and oral bioavailability. In addition to that, even more preferred compounds of the present invention show further advantageous properties that are beneficial for their use as medicaments, such as desirable pharmacokinetic profiles that provide suitable metabolic stability and oral bioavailability, and at least one additional advantageous property chosen from an advantageous cardiovascular profile and a suitable CYP inhibition profile.